Based on the Sen spacetime, the orbital energy and angular momentum are calculated, and the solution for the motion of a test particle derived to the second post-Newtonian order. The effect of the Sen black hole's charge q m $q_{m}$ on the periastron advance and orbital period is obtained. In particular, it is found that q m $q_{m}$ has an influence on perihelion precession at both the first and second post-Newtonian orders, whereas its effect on the orbital period is confined solely to the second post-Newtonian order. Finally, the precession of the star S2 is...
